A drill bit for directly drilling into the bedrock and collecting bedrock core sample (core) has been used with a matrix that is appropriately designed in order to estimate distribution and deposits of mineral resources. In this case, the matrix of the drill bit is a part that directly contracts the bedrock and drills into the bedrock and includes diamond abrasives therein.
In general, a drill bit includes a matrix part that is manufactured using a typically called “infiltration process” of forming a mold by mixing diamond and metal powder such as tungsten (W), molybdenum (Mo), and cobalt (Co), heating a metallic binder in a state of an alloy or single metal such as copper (Cu), tin (Sn), nickel (Ni), and manganese (Mn) to a melting point or more, and filling the mold with the metallic binder according to capillary force. The matrix part is connected to a backing part for fixing a shank (steel body) and is integrally manufactured via one number of times of infiltration process to complete a drill bit. In general, with regard to manufacture of a drill bit, about 1,000° C. or more as a melting point of a metallic binder is maintained while a shank is inserted into a matrix in a molding state and an upper end of a backing part and, thus, the shank inevitably experiences high temperature in order to manufacture a core bit and, in this case, the hardness of the shank is degraded.
As such, a shank performs a function of fixedly supporting a matrix in a drill bit used to drill into various types of bedrocks and, accordingly, should not be abraded until the matrix is completely consumed. However, in an actual working area, a shank may be remarkably abraded and a diamond tip may not be completely consumed and, in a serious case, the shank and the matrix may be separated and detached during a drilling operation and left in a drilling hole, which does immense damage to the drilling operation.
In order to prevent a shank from being abraded, particles with high hardness are attached on a surface of the shank in the form of a band to alleviate an abrasion degree of the shank, but the alleviated degree is not high. In addition, the shank is formed of alloy steel with high hardness to alleviate an abrasion degree, but there is a limit in a width for enhancing hardness according to change in steel type is restrictive and, accordingly, it is difficult to overcome the problem.
Korean Patent Publication No. 10-2014-0022287 (published on Feb. 24, 2014) as the cited reference discloses a core bit for core drilling.